Method of making fin radiators



pril 7, 1936..

W. G. LAIRD METHOD OF MAKING FIN RADIATORS Filed Dec. 8, 1932 `A TTORNEY Patented Api'. 7, 1936 UNITED STATES Maroon or .ammo FIN aanrn'rona wurm o. ran-o, rleasanivrue. u.. r. dpplication cember t, i932, Seriali lilo. timid@ o canna. (ci. cam-iria This invention lrelates to the art or heat erchange, and more particularly to improvements in fin-tube radiators and method of manufacture.

One ot the primary objects of this invention 5 is'to provide a iin-tube radiator having an improved joint of great strength and heat conductivity between the tube and a peripherally mounted iin.`

A further obiect of the invention is to provide io an emcient, rapid and simple method ci assembling iin-tube radiators.

.a still further object ci the invention is to provide a construction and method of assembly tor iln-tube radiators which will materially improve l5 their appearance and reduce their cost without sacrice oi heat transfer capacity. feature ot the invention is the production oi" a radiator oi the rintube type embodying radiating tins ot very thin section and relatively 2d large radiating surface mounted transversely in spaced parallel relation on the tube, with an edge of each nn imbedded deeply in the metal wall of the heating tubaand with a inetal-to-rnetal joint area `between tube and iin surface substantially equal to the full imbedded surface area oi' the iin.

With these and other objects and features in view, the invention consists ofthe improved heat exchanger and method of assembly hereinafter 30 described and more particularly defined in the accompanying claims.

lin the following detailed description ci' the invention, reference will be made to the'acconr n planying drawing, in which: 3e Fig. lis a top plan view of the improved hn tube radiator.

Fig. 2 is an end view ci the radiator ci Fig. l. Figs.v 3 and t illustrate two forms oli `.split tins adapted ior use in the radiator assembly of Fig. l. Fig. ii is an enlarged side elevation, partly in longitudinal section, of a portionkof a tube showvhns loosely seated in peripheral grooves there'- oi preparatory to assembly. i'

Fig. is a transverse vertical section of the heating" tube taken along the line of Fig. 5. Fig-fil? is a view corresponding to that of Fig. 5 illustrating-,the way in which therfins are imbedded in the tube walls after assembly,

'go ,-.yFig 8 is an enlarged side elevation, partly in longitudinal section, oi-a portion ora tube havin ggaj helical groove in its outer wall. l "'Figs. 9 and :l0 are respectively brolren side and a end elevations of one form of partially split un 55 adapted iormounting on the tube oi Fig. t.

Figs. ll and 12 are respectively broken side and end elevations oi another torni ot split hn adapted for mounting on the tube ol' Fig. d.

vThe heat exchanger ol' the present invention is generally assembled from a periphera-lly grooved a tube and a plurality ot sheet metal uns. .in assembling the radiator the general procedure is to seat an edge of one or more dns in each peripheral groove and then to apply pressure to the tube walls in a direction substantially at right to angles to the faces of the seated hns to thereby crush the walls oi. the groove inwardly into tight gripping contact with each unit area of imbedded dn surface.`

iFine embodiment oi -the heat exchanger which iii is illustrated inl the drawing, comprises a Ltlntube radiator (Fig. l) having a plurality oi split apertured sheet metal :fins it mounted transversely in spaced parallel relation on a heating tube it, with the central aperture edges ot the 2o uns encircling and imbedded in the wall oi the tube. The tube itis shown as a straight tube section enlarged at both ends to form threaded male and female coupling nipples titl and i222 adapted for connection in a steam or other lipid 25 heating system. as shown in Figs. 3 and ii, the iins it may be split along planes passing horizontally or vertically through the central aperture it, thus forming matched lln sections tit and Stil (Fig. 3) and (Fig. d). 'Fliese matched 30 n sections are clamped in the tube walls to i'orm in the assembled radiator the full equivalent oi a single centrally apertured rectangular fin; and to simplify the description of the invention, the matched nn sections of Figs. 3 and 1i and the par- 35 tially split hns oi. Figs. 9-12 will be generally delined throughout the description by the term apertured split iin. The tins are split in order to facilitate rapid mounting thereof on the tube it?.

Preparatory to assembly, the tube iti is formed 4@ with peripheral grooves liti (Fig. 5) in its wall. The grooves are made wide enough so that the inner edges tt of the uns are readily seated therein as a preliminary step in assembling the radiator. In the tube design ot Fig. 5, the outer wall 4&5 of the heating section or the tube has a plurality ot uniformly spaced circumferential endless grooves, while the tube oi Fig. t is formed with a single encircling helical groove hag a pitch substantially the same as the spacing of adjacent 50 grooves of Fig. 5.

The main heating section of tube it, on which the ins are mounted, may have any cross-sectional shape, with the central apertures it ci the tins cut to contorni closely in contour and dimen- 55 sions with the base of the groove I8 on which the inner edge of the nn is to seat. Several advantages result from employing a tube of teardrop" section (Fig. 6). 'I'he apertures 26 of the flns shown in Figs. 3 and 4, are cut to fit the grooves of the tear-drop sectioned tube shown in Fig. 5. The split fin of Fig. 3 has a folded or double lapped grommet section 40 adjacent its inner edge, for the twofold purpose of reinforcing the n and increasing somewhat the area of the neck through 'which heat is conducted from the tube to the iin.

The manner in which the radiator is assembled permits the use of very thin4 sheet copper inV making up the flns. The complete radiator is very compact and light in weight for a given heating surface. Hard rolled sheet copper of 1/100-inch thickness is a suitable material for the fins, while the heating tube may be made of steel or--aluminum. The largest internal diameter of the tube may be less than 1", with a wall thickness of :about 115 inch. The peripheral grooves in the tube walls may have 'a rectangular section of about/ 100 inch in depth,-or the grooves may fhave sides tapering from a width of, say, 4/ 100 inch at the top of the groove to 3/ 100 inch at the Ibase. The commercial form of the radiator as designed for use in steam heating systems can be :assembled into units 'of any desired capacity and length by coupling together sections chosen from -two standard'le'ngths measuring lrespectively 12" .The rst step in the preferred method of assembling the radiator of Fig. 1, as illustrated in Fig. 5, involves seating the aperture edges of each matched half section of a split n in a corresponding groove on the heating tube. To facilitate the performance of this assembly step, the upper half sections 32 (Fig. 4) of all of the fins required for the unit may have their edges 38 loosely seated in the grooves of the heating tube, after which the unit is turned over so that the weight of the unit holds the seated sections in place, while the matched lower sections 34 in turn have their inner edges seated on the groove. Thisoperation when completed brings the upper and lower section of each split iin in contact along the edges abutting the plane of the split 24-24. The loose seating of the inner edges of the split -ns in the peripheral grooves of the tube can be readily accomplished, as will be understood, by automatic machinery.

In assembling radiators employing tubes with a continuous helical groove encircling their periphery, of the type illustrated in Fig. 8, partially split fins may be employed, such as those shown in Figs. 9-12.

Such fins may consist of apertured rectangular plates partially split along a radial line 46 extending outwardly from the inner edge 38 of the plate. After the plates are partially split as shown, the inner or aperture edge of the fin is distorted by spreading apart the corner-of the split edge (Figs. 10, 12) to impart to the inner edge ofthe iin a contour and helical pitch match- ,in all directions. the operation .more than 10% of its originalA ing that of the groove in the tube wall. To loosely seat the partially split ilns as thus shaped in parallel spaced transverse relation in the groove, the fins are successively threaded onto the tube from one or both ends.

To allow for.this method of assembly, the coupling nipple on at least one end of the heating tube will normally be reduced in size to permit be partially split along a plurality of spaced radial line's, and the edge then pressed outwardly to form a split frusta-conical flange as illustrated by plate il of Fig. 5. After placing such fins in spaced relation on the tube with their inner edges 38 engaging an upper edge of the groove, pressure is applied laterally thereto to straighten the fin and loosely seat the inner edge thereof in the base of the groove.

After all of the split fins have been mounted in spaced relation on the heating tube with their inner edges loosely seated in the peripheral grooves, as above described, the tube with its loosely tted fins is placed in a press having a frame adapted to'hold the fins in their groove seats, each fin with its inner edges resting on the base of the groove. Pressure is then applied to the ends of the tube longitudinally thereof to -thereby shorten the tube sufilciently to crush the metal in the side walls of each groove laterally into substantially 100% area contact with the n surface thus imbedded within the peripheral wall of the tube. During this operation one end of the tube may be held stationary against a die abutment while the other end is movably compressed with all of the metal in the tube walls shifted toward the stationary end, or squeezing tube crushing operation results in clamping the inner edges of the split fins into substantially integral structure with the tube walls. Each unit of surface area of the fins extending within the tube wall is gripped almost simultaneously with every other unit of imbedded fin area by the inwardly crushed side walls of the grooves, so that the operation causes no substantial distortion of the n or shifting of metal from one imbedded portion thereof to another. The resulting joint between fin and tube is strong and has a very high heat conductivity coefficient, since the heat conductivity neck between iin and tube substantially corresponds in area with the imbedded surface area of the iin. The metal of the heating tube so 'closely adheres to the fins as to form -a substantially seamless connection. Heat conduction between the fin and tube therefore takes place without interference, rapidly and uniformly The tube may be shortened by the apertured fins to slip over it for engagement length, and its walls are thickened somewhat, particularly in the plane of the grooves, as indicated by the internal annular ridges IIBA shown in Fig. 7, as formed by crushing of metal below the base of the groove.

' After the tube and ns have been assembled into an integral radiator unit by the longitudinal squeezing operation on the tube, the unit is removed from the press. Side plates 50 may then be mounted along the lateral edges of the ns but spaced therefrom to prevent scraping thereof during expansion. The end plates are attached to the side plates 42 and reinforcing plates M to form a protecting frame for the fins. The side plates also function to strengthen the radiator against mechanical and temperature distortion.`

The heating tube with its grooves, threaded end couplings, and end plates may be die-cast as a unitary integral body. The preferred method of assembly contemplates locking the multiple sheet metal fins in the grooves of the unit by a single longitudinal squeezing operation on the tube. The assembled radiator unit has a relatively much greater metal to metal joint contact area between n and tube than any other known heat exchange device. The type of joint between fln and tube is such that a great variety of metals can be joined, including steel and aluminum, brass and steel, and brass and aluminum.

The invention has been particularly described with relation to heat radiators employing straight tubular heating medium conduits of tear-drop cross section. It will be apparent, however, that the invention is generally applicable to heat exchange apparatus in which the flow of heat may be in either direction between the ns and heating element. Moreover the heating element need not be limited to any particular external or internal shape or section. For example, if the source of heat used is electrical current, the heating element need not be tubular providing that its length and cross section do not exceed the limits within which the walls .of grooves in its periphery can be crushed to imbed iins seated therein, without undue distortion of the resulting radiator.

I claim:

1. The method of joining a radiator iin to a tubular heat exchange element which comprises, forming a groove in the wall of said element, inserting an edge of the iin therein, and-"crushing the walls of the groove against the embraced sides of the iin by application of a squeezing pressure to the element in a direction at substantially right angles to the groove and in'amount suilicient to permanently shorten the element in the direction in which pressure is applied.

2. The method of assembling a perlpherally grooved heat conductor and a sheet metal iin into an integral heat exchange body, comprising seating an edge. of the n inthe groove of the con.

ductor, and 4applying pressure to the conductor at right angles to the inserted fin surface of sufficient intensity to permanently shorten the conductor vin the direction of pressure application and thereby crush the metal forming the walls of the groove inwardly against each unit area of imbeddedn surface.

3. The method of assembling a peripherally grooved tubular heat conductor and a plurality of sheet metal fins into an integral iin radiator which comprises, mounting said ns in spaced parallel position along the conductor, seating an edge of each fin in a groove of the conductor,

and applying pressure to the conductor at right angles to the inserted n surface of sufficient intensity to permanently shorten the conductor in the direction of pressure application and to thereby crush the metal forming the walls of the grooves inwardly against each unit area of imbedded n surface.

4. The method of assembling a peripherally grooved metal tube and a sheet metal fin into an integral heat exchange unit, comprising seating an edge of the iin in the'groove of the tube, and applying a squeezing pressure to the ends of the tube to thereby permanently crush the metal forming the walls of the groove into full metal to metal contact with the imbedded surfaces of the n.

5. A method of assembling into a iin-radiator a heating tube having spaced parallel circumferential grooves in its outer wall, and a plurality of split sheet metal fins each having an inner edge corresponding in contour and dimensions with the base of a groove, comprising mounting the fins transversely on the tube with an inner edge of each fin loosely seated in a corresponding groove, and applying a crushing pressure to the tube walls coaxially thereof, to thereby permanently shorten the tube and simultaneously cold-press the walls of all the grooves into intimate heat-conducting contact with the inserted fins.

6. The method of assembling into a radiator a heating tube having a helical groove formed in its outer peripheral wall, and a plurality of partially split sheet metal fins having inner edges correspending in contour an-d dimension with the base of said groove, comprising successively threading a plurality of the fins onto the tube in transverse parallel relation along the groove, and applying a crushing pressure to the ends of the tube longitudinally thereof to thereby permanently shorten the tube and force the metal forming the walls of the groove into intimate heat-conducting contact with the imbedded portion of each fin.

7. 'I'he method of assembling a radiator including as elements a heating tube having a groove in its peripheral wall and a sheet metal fin having an inner edge conforming in contour and dimensions with the base of said groove, which comprises mounting the fin on the tube with its inner edge seated in the groove, and applying pressure to the ends of the tube to force the same toward each other and thereby form a mechanically strong and heat-conductant joint between the tube wall and the groove seated edge of the fin.

8. The method of manufacturing a 1in-tube radiator which comprises, diecasting a straight metal tube section with integral peripheral grooves, loosely seating an inner edge of each of a plurality of thin metal fins in said grooves in spaced parallel relation to each other and, applying pressure to the ends of the tube of sufficient intensity to squeeze the ends toward each other and crush the side walls of the grooves into full metal to metal contact with imbedded surfaces of the ns.

9. The method of assembling a perlpherally grooved tubular metal heat-conductor and a sheet metal iin into an integral heat exchange body,

comprising, seating an edge of the iin in the groove of the conductor, and applying compression stress to the conductor coaxially thereof in amount suicient to permanently shorten the same and squeeze the metal of the conductor inwardly against the imbedded n surface.

WILBUR o. 

